Photohalogenation of hydrocarbons



April 16, 1968 T. HuTsoN, JR.. ETAL 3,378,476

PHOTOHALOGENATION OF HYDROCARBONS Filed March 12, 1964 Komm QHE .$5.3 "SME S1015 "SME Y o9 m SE o? om oN O- O o O. XQG-4 SBGI'HO'IHDICI O L SSGIHO'IHDONOWOILVH .LHDIBM INVENTORS THOMAS HUTSON,JR. BY A. D. HOLIDAY l A T ToR/vErs United States Patent Olice 3,378,476 PHOTOHALOGENATION F HYDROCARBONS Thomas Hutson, Jr., and Allan D. Holiday, Bartlesville,

Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Filed Mar. 12, 1964, Ser. No. 351,480 7 Claims. (Cl. 204-163) ABSTRACT OF THE DISCLOSURE The ratio of monohalogenated hydrocarbons to dihalogenated hydrocarbons, in the light catalyzed halogenation of liquid hydrocarbons containing about 8 to 20 carbon atoms per molecule, is increased by conducting the halogenation in the presence of an aromatic hydrocarbon containing not more than 7 carbon atoms per molecule.

This invention relates to the halogenation of hydrocarbons. In one aspect this invention relates to a novel method for producing monohalogenated hydrocarbons in a high yield with respect to dihalogenated hydrocarbons. Another aspect of this invention relates to a method for producing monohalogenated hydrocarbons in high yield without sacrice of a high ratio of monohalogenated hydrocarbons to dihalogenated hydrocarbons.

The halogenation of hydrocarbons is known and has been accomplished in both -gaseous and liquid phases; thus the production of chlorinated, brominated, iodinated and fluorinated hydrocarbons has been accomplished. Light and particularly ultraviolet light is a known catalyst for the halogenation of paratin hydrocarbons. The production of monohalogenated hydrocarbons has been dificult because the halogenation reaction occurs stepwise and is not an equilibrium reaction so that, given sufficient residence time and suicient halogen at reaction conditions, the reaction product would contain no monohalogenated hydrocarbons at all. For many uses, such as the production of linear detergent alkylate, made from alkyl chlorides containing from 7 to 15 carbon atoms, a monohalogenated, c g., monochlorinated, hydrocarbon is required as the starting material.

According to the invention the ratio of monohalides to dihalides in the lighcatalyzed halogenation of a liquid hydrocarbon containing 8 to 20 carbon atoms per molecule can be increased substantially by conducting the halogenation in the presence of an aromatic hydrocarbon containing not more than 7 carbon atoms per molecule. The amount of aromatic employed will usually be about l to 60 weight percent of the total hydrocarbon feed, preferably about to 50 weight percent; however, beneicial results are obtained when less than l percent aromatic is present in the feed, for example 0.1 or 0.5 weight percent aromatic. There is no upper limit to the amount of aromatic to be used except that dictated by economy. The use of a diluent in a reaction increases the size of the equipment required to produce a given quantity of prod ucts or conversely reduces the amount of reactant that can be processed in a given piece of equipment. Thus, the suggested upper limit of 60 weight percent aromatic in the hydrocarbon feed is an economic limitation rather than a process limitation as evidenced by the excellent results obtained with I82 weight percent aromatic in a hydrocarbon feed stream.

It is an object of this invention to provide a method and means for producing monohalogenated hydrocarbons in high yield. Another object of this invention is to provide a method for halogenating a parain hydrocarbon to produce a high ratio of monohalogenated hydrocarbon to dihalogenated hydrocarbon. Still another object of this invention is to provide an improved method for pro- 3,378,476 Patented Apr. 16, 1968 ducing normal dodecyl monochloride in a high ratio with respect to normal dodecyl dichloride.

The halogenation reaction is catalyzed by light and where it is practical sunlight can be utilized; however, it is usually more satisfactory to employ articial illumination so that the amount of illumination can be controlled and maintained constant. The reaction is usually carried out in a transparent reaction chamber fabricated from quartz, glass or other materials transparent to light waves. An opaque reactor can be employed if transparent windows are provided. Lamps are usually employed to provide illumination in the range of about 3,650 to 6,000 Angstrom units. This range includes visible light and ultraviolet light.

In carrying out the process of this invention a parat-lin hydrocarbon containing from about 8 to about 20 carbon atoms per molecule together with the desired amount of aromatic hydrocarbon is saturated with a halogen, e.g., chlorine, in the dark and at about room temperature and is then passed through a reaction chamber and exposed to the activating influence of light to effect the halogenation reaction.

It has been found desirable to perform the halogenation reaction in stages with cooling, removal of hydrogen halide and resaturation with halogen between stages. This stepwise hal-ogenation of paraffin hydrocarbons is described in copending application Ser. No. 248,543, filed Dec. 3l, 1962, by Thomas Hutson, Jr. and R. A. Loth.

Aromatic hydrocarbons applicable for use in the invention include Ibenzene and toluene which contain 6 and 7 carbon atoms respectively. Thus, aromatic hydrocarbons having a maximum of 7 carbon atoms per molecule can be used in the invention.

lt is presently not known why benzene, or toluene, has the demonstrated effect on the ratio of monohalides to dihalides in the chlorination product but the phenomenon does appear to Ibe specific to benzene or toluene. Other solvents or diluents such as carbon tetrachloride, carbon disulde, poly-substituted 4benzene compounds, and the like have not been found to affect the ratio of monohalides to dihalides appreciably.

The improved etiiciency of the halogenation reaction can be utilized in at least two ways: At constant halogenation conversion a lower yield of dichlorides is obtained which results in a lower yield of byproduct heavy alkylate in the alkylation step which follows the halogenation step; and at constant monohalide to dihalide ratio the halogenation conversion can be increased. In either event when benzene is utilized in the halogenation step the benzene, as well as the chlorination product, is utilized in the alkylation step that follows. A small amount of benzene is also halogenated and passes through the alkylation step unchanged if contaminants are present, such as iron, which catalyzes chlorination of benzene. This halogenated benzene can be removed from the alkylate in the nal purication (fractional distillation) of the product. -It has been found that with 20 percent benzene in the normal dodecane feed to a light catalyzed chlorination reaction the chlorination conversion is doubled without changing the ratio of monochloride to dichloride. Thus, the product of -rnonochloride was increased without a corresponding increase in feed rates or equipment size. Doubling the chlorination conversion would reduce the paratlin hydrocarbon recycle by about 6() percent and the size of the chlorinator by 40 percent when producing a iixed quantity of alkylate.

The following examples will be helpful in attaining an understanding of the invention. The following examples are intended to be illustrative and should not be so construed as to limit the invention unduly.

3 Example I Normal dodecane (n-C12H26) was saturated with elemental chlorine in the dark and at room temperature. The chlorine-saturated dodecane was then passed through a quartz tube and subjected to the rays from an ultraviolet light lamp. A stream composed of 18 weight percent dodecane and `82 weight percent benzene was similarly saturated with elemental chlorine in the dark and at room temperature and then passed through the quartz tube and subjected t-o the ultraviolet light. Temperatures, pressures, light intensity and other operating conditions were maintained the same in both runs. Analyses of the products of the two runs are shown in the following Table I.

l Product distribution reported on a benzene-free basis.

The above table shows that the ratio of monochlorides to dischlorides in the chlorinated product was more than doubled by utilizing benzene diiuent. Similar runs were made with different amounts of benzene diluent and the results of these runs are shown in the figure of the drawing. Examination of the curves of the drawing show that the ratio of monochlorides to dichlorides is increased by substantially the same amount when 27.3 percent benzene, 47.9 percent benzene or when 82 percent is employed as diluent. It should be noted that the values of Table I are also plotted on the curves shown in the drawing. Some of the runs represented by the points on the curves of the drawing were made with sunlight and some were made with the ultraviolet lamp. No difference in chlorination has been determined whether sunlight or ultraviolet light is used to catalyze the reaction.

Example II are shown in the following Table II.

TABLE II Component Without Toluene, With wt. percent percent Toluene l 87.8 91.4 l0. 9 8. 1 i 1.3 0.5 Ratio Mono/di 8.4/1 16. 2/1

1 Product distribution reported on a toluene-free basis.

The addition of l0 percent toluene to the tetradecane substantially doubled the ratio of monoto dichlorides.

Although the stepwise process of application Ser. No. 248,543 is preferred, the invention is not limited to such process but is applicable to any halogenation of hydrocarbons process.

That which is claimed is:

1. In the process of halogenating a liquid parain hydrocarbon having about 8 to 20 carbon atoms per molecule wherein the hydrocarbon is reacted with a halogen in the process of light, the improvement comprising conducting the halogenation reaction in the presence of 5 to 50 weight percent of an aromatic hydrocarbon containing a maximum of 7 carbon atoms per molecule.

2. The process of claim 1 wherein the aromatic hydrocarbon is benzene.

3. The process of claim 1 wherein the aromatic hydrocarbon is toluene. l

4. The process of halogenating a liquid paraffin hydrocarbon having about 8 to 20 carbon atoms per molecule which comprises admixing said paraffin hydrocarbon with 5 to 50 weight percent of an aromatic hydrocarbon having a maximum of 7 carbon atoms per molecule; substantially saturating the mixture of parain and aromatic hydrocarbon with an elemental halogen at about room temperature and in the dark; subjecting the mixture to the action of light rays for a time sufticient to react substantially all of the halogen; and removing hydrogen halide from the resulting product.

5. The process of chlorinating n-dodecane which comprises admixing benzene with n-dodecane to form a hydrocarbon mixture containing 5 to 50 weight percent benzene; substantially saturating the mixture with chlorine at about room temperature and in the dark; subjecting the chlorine-saturated mixture to light rays for a time sufficient to react all of the chlorine; removing HCl and n-dodecane dichloride from the resulting product; and recovering n-dodecane monochloride in a mixture of ndodecane and benzene as a product of the process.

6. The process of chlorinating n-tetradecane which comprises admixing -toluene with n-tetradecane to form a hydrocarbon mixture containing about l to 60 weight percent toluene; substantially saturating the mixture with chlorine at about room temperature and in the dark; subjecting the chlorine-saturated mixture to light rays for a time sufficient to react all of the chlorine; removing HCl and n-tetradecane dichloride from the resulting product; and recovering n-tetradecane monochloride in a mixture of n-tetradecane and toluene as a product of the process.

7. The process of chlorinating n-dodecane or n-tetradecane which comprises admixing benzene or toluene with the n-dodecane or n-tetradecane to form a hydrocarbon mixture containing 5 to 50 weight percent benzene or toluene; substantially saturating the mixture with chlorine at about room temperature and in the dark; subjecting the chlorine-saturated -mixture to light rays for a time suicient to react all of the chlorine; removing HC1 and n-dodecane dichloride or n-tetradecane dichloride from the resulting product; and recovering n-dodecane monochloride or n-tetradecane monochloride in a mixture of n-dodecane or n-tetradecane and benzene or toluene as a product of the process.

References Cited UNITED STATES PATENTS 2,370,342 2/1945 Zellner 204-163 2,707,197 4/ 1955 Souillard 204-163 2,948,667 8/1960 Lirnido et al. 204-163 HOWARD S. WILLIAMS, Primary Examiner,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,378,476 April 16, 1968 Thomas Hutson, Jr., et al. It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 5, for "process" read presence Signed and sealed this 24th day of June 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

